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1992 454 TBI Fuel Pressure HELP

Hello, on my 1992 454 motorhome, when i turn the key to on position the fuel pressure builds up to about 12 psi, I can hear the pump coming on then after two seconds roughly the pump turns off and the pressure drops back own to zero. I pinched off the fuel return line and it still does it. I pinched off the feed line after it builds up and it still drops after the pump turns off.

My sources say that pressure should stay up even after two hours. Well, the pump is brand new, the regulator is new and so is the fuel pump relay! The car runs fine. So my sources say there must be a leak either outside or inside the tank but if so why when I pinch off the feed line does pressure still drop?

yes. when i climb a hill the exhaust manifolds start to glow within 30 seconds. we cup the tbi shut restricting air flow in and the glow goes away so it's been confirmed that I have
a fuel delivery issue. no exhaust blockage, new catalytic. timing is good, engine has been rebuilt in fact with timing chain and new exhaust manifolds. no vacuum leaks and i put in a new
fuel pump, a new pump relay and the fuel pressure regulator has been rebuilt also. I am seriously amazed why this is happening but it cranks over right away good power. Even the computer
has been replaced.

What's your pressure dropping to when the manifolds start to glow? If the pressure is dropping when it glows, then maybe you have a kinked fuel line or some other type of restriction that allows decent pressure except at higher flow rates? I had an '89 454 Crew Cab 4x4 for a while and it always got pretty hot on the hills too, even though there was nothing wrong with my fuel system. I'm not sure how well GM tuned the 454 TBI for heavy loads. I didn't keep it long enough to really dig into it, though.

yes. when i climb a hill the exhaust manifolds start to glow within 30 seconds. we cup the tbi shut restricting air flow in and the glow goes away so it's been confirmed that I have
a fuel delivery issue. no exhaust blockage, new catalytic. timing is good, engine has been rebuilt in fact with timing chain and new exhaust manifolds. no vacuum leaks and i put in a new
fuel pump, a new pump relay and the fuel pressure regulator has been rebuilt also. I am seriously amazed why this is happening but it cranks over right away good power. Even the computer
has been replaced.

my thermostat was upside down ran hot when I pulled up one hills in flagstaff till the fan started pumping I could bet on it staying in open closed loop check your vacuum at idle and timing I swear my vac was like 30-40 in so I put a lot in it oh it was hot could cook dinner at idle

Maybe try setting the Power Enrichment (PE) Delay or Wide Open Throttle Delay to ZERO seconds in the PROM Chip. See attached screen shot showing BCC BAMM with a WOT delay of 70 seconds! PE is similar to having the secondary's of a 4 barrel carburetor opening up.

IMO you have confirmed that a richer mixture does not cause the manifolds to turn red, but you have not confirmed a fuel delivery problem. Do you have access to datalogs or scantool readings? Have you confirmed the timing is actually set where it shuld be set?

I have to guess the last owner of my truck was trying to get better mileage since there was one of the wrong injectors in it when pulled the radiator i found what I think is the right big block injector but it's so rusted I can't use it anyway smh!